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  <div class="section" id="uniform-excitation">
<span id="uniformexcitation"></span><h1><span class="section-number">3.1.7.2. </span>Uniform Excitation<a class="headerlink" href="#uniform-excitation" title="Permalink to this headline">¶</a></h1>
<p>The UniformExcitation pattern allows the user to apply a uniform excitation to a model acting in a certain direction. The command is as follows:</p>
<dl class="function">
<dt>
<code class="sig-name descname">pattern UniformExcitation $patternTag $dof -accel $tsTag &lt;-vel0 $vel0&gt; &lt;-fact $cFact&gt;</code></dt>
<dd></dd></dl>

<table class="colwidths-given docutils align-default">
<colgroup>
<col style="width: 17%" />
<col style="width: 17%" />
<col style="width: 67%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Argument</p></th>
<th class="head"><p>Type</p></th>
<th class="head"><p>Description</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>$patternTag</p></td>
<td><p><em>integer</em></p></td>
<td><p>unique tag among load patterns</p></td>
</tr>
<tr class="row-odd"><td><p>$dof</p></td>
<td><p><em>integer</em></p></td>
<td><p>dof direction the ground motion acts</p></td>
</tr>
<tr class="row-even"><td><p>$tsTag</p></td>
<td><p><em>integer</em></p></td>
<td><p>tag of the TimeSeries series defining the acceleration history.</p></td>
</tr>
<tr class="row-odd"><td><p>$vel0</p></td>
<td><p><em>float</em></p></td>
<td><p>the initial velocity (optional: default=0.0)</p></td>
</tr>
<tr class="row-even"><td><p>$cFact</p></td>
<td><p><em>float</em></p></td>
<td><p>constant factor (optional: default=1.0)</p></td>
</tr>
</tbody>
</table>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>The responses obtained from the nodes for this type of excitation are <strong>RELATIVE</strong> values, and not the absolute values obtained from a <span class="xref std std-ref">multiSupportPattern</span>. This is a consequence of the equation of motion being solved:</p>
<div class="math notranslate nohighlight">
\[M\ddot{U} + C\dot{U} + K U = P(t)\]</div>
<p>and how the loads are applied with this load pattern.</p>
<div class="math notranslate nohighlight">
\[P(t) = -c_{Fact} M l \ddot{u_g}\]</div>
<p>where <span class="math notranslate nohighlight">\(l\)</span>’ is a vector of <strong>1</strong>’s and <strong>0</strong>’s, with a <strong>1</strong> corresponding to all matrix equations in the <strong>$dof</strong> degree-of-freedom direction and <strong>0</strong> for all other degrees-of-freedom. The <span class="math notranslate nohighlight">\(\ddot u_g\)</span> is obtained from the time series.</p>
</div>
<div class="admonition-example admonition">
<p class="admonition-title">Example:</p>
<p>The following example shows how to construct a <strong>UniformExcitation</strong> pattern with a tag of <strong>2</strong> acting in the <strong>1</strong> direction. The acceleration for the pattern comes from the <a class="reference internal" href="pathTimeSeries.html#pathtimeseries"><span class="std std-ref">Path TimeSeries</span></a> with tag <strong>3</strong> which has been created using the contents of the <strong>elCentro.dat</strong> file, a <span class="math notranslate nohighlight">\(\delta t = 0.02\)</span>, and a scale factor given by the variable <strong>g</strong>, which has been set to <strong>386.1</strong>.</p>
<ol class="arabic simple">
<li><p><strong>Tcl Code</strong></p></li>
</ol>
<div class="highlight-tcl notranslate"><div class="highlight"><pre><span></span><span class="k">set</span> g <span class="mf">386.1</span>
<span class="nv">timeSeries</span> Path <span class="mi">3</span> <span class="o">-</span>filePath elCentro.dat <span class="o">-</span>dt <span class="mf">0.02</span> <span class="o">-</span>factor <span class="nv">$g</span>
<span class="nv">pattern</span> UniformExcitation  <span class="mi">2</span> <span class="mi">1</span> <span class="o">-</span>accel <span class="mi">3</span>
</pre></div>
</div>
<ol class="arabic simple" start="2">
<li><p><strong>Python Code</strong></p></li>
</ol>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">g</span> <span class="o">=</span> <span class="mf">386.1</span>
<span class="n">timeSeries</span><span class="p">(</span><span class="s1">&#39;Path&#39;</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s1">&#39;-dt&#39;</span><span class="p">,</span> <span class="mf">0.005</span><span class="p">,</span> <span class="s1">&#39;-filePath&#39;</span><span class="p">,</span> <span class="s1">&#39;A10000.dat&#39;</span><span class="p">,</span> <span class="s1">&#39;-factor&#39;</span><span class="p">,</span> <span class="n">g</span><span class="p">)</span>
<span class="n">pattern</span><span class="p">(</span><span class="s1">&#39;UniformExcitation&#39;</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">&#39;-accel&#39;</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
</pre></div>
</div>
</div>
<p>Code Developed by: <strong>fmk</strong></p>
</div>


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